Innovative rainwater solution launched to address record rainfall in Denmark

Denmark experienced unprecedented rainfall in 2023, breaking historic records, and faces ongoing challenges such as rainwater and flooding of roads and basements. Rather than relying on CO expansion₂Professor Marina Bergen Jensen from the University of Copenhagen suggests managing rainwater at the source and treating it as a valuable resource.

In response to the increasing frequency of heavy rainfall, many Danish cities are considering major sewerage expansion projects. However, Professor Marina Bergen Jensen argues that this traditional approach is outdated.

Her research focuses on the implementation of nature-based solutions for urban stormwater management to reduce stress on wastewater systems and promote resilience to both floods and droughts. It emphasizes the need to capture rainwater locally near buildings and roads.

“We seem to only see one aspect of extreme climate: too much water. We forget that there can also be too little water, and that water is a resource. “Instead of expanding sewers and building giant concrete tunnels and troughs, we need to manage rainwater locally around individual buildings and roads, because rainwater itself contributes to global warming.” says Professor Marina Bergen-Jensen from the School of Geosciences and Natural Resource Management.

“In this way, we can increase our resilience to both floods and droughts while reducing pressure on our sewage systems.”

Professor Jensen acknowledges that implementing nature-based solutions, known as rainwater-NbS, presents challenges as they often require additional space. However, Professor Jensen and his colleagues have developed an innovative technology that outperforms both conventional sewer extensions and first-generation spaces that require stormwater-NbS solutions.

3 meter high willow garden fence

Disguised as a 10-foot-tall willow garden fence, this revolutionary invention has been dubbed the Green Climate Screen. This solution has already been successfully implemented in the Valby district of Copenhagen. The Green Climate Screen also acts as a sound barrier, managing runoff from the roofs of adjacent buildings and redirecting water upward towards the screen instead of sending it to the sewer system.

This system uses gravity to channel roof water to the top of the fence, where it is absorbed into the central material. The water then evaporates through the climate screen, providing an efficient and sustainable solution. When it rains heavily, excess water can be stored in the adjacent lawn, demonstrating the system’s ability to withstand extreme weather conditions that exceed a once-in-100-year downpour.

“The system harnesses the potential energy of roof water to channel water away from the building and into a free-standing green climate screen, from where it can evaporate, seep, or drain into adjacent areas surrounded by shallow earthen embankments. ,” explains Marina. Bergen Jensen.

Importantly, Green Climate Screen accomplishes all this without the need for soil excavation, pumping, or concrete. According to Professor Jensen, this opens up new possibilities for implementing effective rainwater solutions even in confined spaces.

In addition to noise reduction, Green Climate Screens can also offer other unique opportunities, such as linking with biodiversity, recreational areas, or urban cooling efforts.

Expansion of local systems

Professor Jensen points out that local systems like green climate screens need to be widely implemented to have a big impact on stormwater management. Social housing or co-operative housing associations may be a good starting point here. However, she emphasizes the need for legal support, guidance and financial incentives for landowners to facilitate the transition to these innovative solutions.

“You can also start by introducing it into social housing and co-operative housing associations, which are often well-organized and responsible and have large rooftops and green spaces that benefit from water. Hopefully we will go a long way,” says Marina Bergen Jensen.

Operational details of the Green Climate Screen include managing rooftop runoff through an open vessel principle, distributing rainwater along the length of the screen, and utilizing mineral wool to absorb and evaporate water. The system is designed to withstand up to 10 years of rainfall and is capable of extreme rainfall in line with Copenhagen’s cloudburst plan for once-in-100-year rainfall (90 mm in 24 hours) can.